1. Field of the Invention
This application pertains to self-propelled upright vacuum cleaners. More specifically, this invention pertains to the manner in which the agitator chamber, which typically defines the floor nozzle, and the hard bag or handle portion of the vacuum cleaner are independently pivotally attached to the main frame of the vacuum cleaner with offset pivot axes.
This invention also pertains to an upright vacuum cleaner having a structure for automatically engaging and rotating the agitator when the bag housing is located in a generally inclined operating position and automatically disengaging and stopping rotation of the agitator when the bag housing is located in the upright storage position, which structure may also be manually actuated to maintain disengagement of the agitator for cleaning bare floors.
2. Description of Related Prior Art
Self-propelled upright vacuum cleaners conventionally include an electric motor that drives a fan for generating a vacuum, an agitator for agitating the carpet, and at least one drive wheel for propelling the cleaner over the floor. In order to propel the cleaner in both forward and reverse, self-propelled vacuum cleaner's typically contain a transmission having an input shaft that is drivingly connected to the motor's output shaft via a drive belt or by gears. The transmission is selectively controlled by the operator to convert the unidirectional input to the transmission into forward and reverse rotation at the transmission's output shaft. Drive is then transferred from the transmission's output shaft to the drive wheel(s).
In order to ensure that the vacuum cleaner is positively and smoothly driven in forward and reverse while traveling over an uneven floor surface, the drive wheels are frequently mounted to the main frame of the cleaner and the lower end of the handle portion of the vacuum cleaner is pivotally mounted to the main frame. With this arrangement, the main frame and the drive wheels can move up and down or "float" relative the handle portion of the cleaner as the cleaner travels over a floor surface and maintain substantially constant contact with the floor. In vacuum cleaners that have the drive wheel(s) mounted to the transmission's output shaft, the entire transmission must be mounted to the main frame in order to enable the drive wheel(s) to float.
In order to maintain the suction nozzle in substantially continuous contact with the floor surface being cleaned, the agitator chamber, which normally defines the floor nozzle, is also typically mounted to the main frame or to the handle portion in a floating fashion. Since the floor nozzle and the drive wheels contact the floor at different locations, the floor nozzle is preferably independently mounted to the main frame or to the handle portion so that the floor nozzle will float on the floor independently of the drive wheels. Thus, the transmission, or at least the drive wheel(s), and the agitator chamber move independently up and down relative the handle portion of the cleaner, so that both the drive wheel(s) and the floor nozzle maintain substantially constant engagement with the floor surface.
U.S. Pat. No. 4,171,554 discloses a prior art self-propelled upright vacuum cleaner that has an agitator chamber and a transmission that are independently mounted to the handle portion of the cleaner for independent up and down motion relative to the lower end of the handle portion. The disclosed transmission is mounted to a first metal frame that is pivotally mounted to the hard bag or handle portion of the upright vacuum cleaner on trunnions extending outward from either side of the lower end of the handle portion. The agitator chamber is likewise mounted to a second metal frame that is also pivotally mounted to the trunnions on the lower end of the handle portion of the vacuum cleaner. The vacuum cleaner's motor is housed in the lower end of the handle portion of the cleaner and the trunnions are located concentrically with the motor's output shaft. Locating the trunnions concentrically with the motor's output shaft enables the transmission and the agitator to pivot about the motor's output shaft. Since the agitator and the transmission pivot about the motor's output shaft, the distance between the motor's output shaft and the transmission and the distance between the motor's output shaft and the agitator remain constant as the agitator and the transmission move up and down relative to the lower end of the handle portion. Maintaining the distances between the motor and the transmission and between the motor and the agitator constant allows simple stretch belts to be employed between the motor and the transmission and between the motor and the agitator for transferring power from the motor to the transmission and from the motor to the agitator.
Manufacturing components out of metal has become undesirable. With modern materials and manufacturing techniques, manufacturing parts out of plastic has become more flexible, efficient and cost effective than manufacturing parts out of metal. Therefore, it is desirable to manufacture a self-propelled upright vacuum cleaner that has a transmission and an agitator chamber that are each independently pivotally mounted on plastic, as opposed to metal, frames. Plastic frames, however, must have thicker walls if they are to have the same strength and rigidity as a metal frame. Thus, if one were to simply manufacture the arrangement disclosed in the previously discussed U.S. Pat. No. 4,171,554 by replacing the metal frames with correspondingly strong and rigid plastic frames pivotally mounted on the trunnions on the handle portion, the necessarily thicker plastic frames would cause the cleaner to be undesirably wide and bulky.